Solution Stability and Sample Preparation

It should be determined if the drug substance being analyzed is stable in solution (diluent). During initial method development an autosampler tray cooler 

The reduction of downtime of the instrument (i.e., operations of pump components, injectors, and detectors) can be controlled to some degree if sample solutions are filtered and/or centrifuged the use of a 0.2- or 0.45-pm-pore-size filter is generally recommend for removal of particulates [15]. Filtration as a preventive maintenance tool for FfPLC analyses is well-documented in the ht-erature [16-18]. 

Sample preparation is a critical step of method development that the analyst must investigate. For example, the analyst should investigate if centrifugation (determining the optimal rpm and time) shaking and/or filtration of the sample is needed, especially if there are insoluble components in the sample. This is usually more prevalent with excipient/DS mixtures and with slurry solutions obtained during the synthesis steps of the API. Syringe filters 

The objective is to demonstrate that the sample filtration does not affect the analytical result due to adsorption and/or extraction of leachables. A word of caution here is that filter studies should be performed to ensure that no adsorption of the compound on the filter is observed. This is particularly the case with protein and peptide samples. Note that for proteins and peptides the impact of centrifugation (speed and time) must be investigated because this may lead to increased aggregate formation. Also, for protein and peptides the initial concentration of the sample could also have an impact on the concentration gradient of the sample in the centrifuge tube, and the concentration of the top, middle, and bottom portions should be assessed. 

Another example includes the recovery (mass %) of API and degradation products of API from two 100-mg tablet (5 tablets) sample solution clarified by filtration and clarified by means of centrifugation. The data in the Table 8-5 demonstrates that the two methods of sample clarification are equivalent and that the filtration procedure (0.2-pm Nylon filter, with 5 mL pre-wet) is 

---